(1) Field of the Invention
The present invention relates to a liquid crystal display device and, more particularly, to a liquid crystal display device with wide viewing angle characteristics of the active matrix system using thin-film transistors.
(2) Description of the Prior Art
Active matrix liquid crystal display devices using active elements as represented by thin-film transistors (TFT) have now been widely used as display terminals of OA equipment since they are light in weight and have a high picture quality equivalent to that of cathode-ray tubes.
The display system of the liquid crystal display devices can be roughly divided into two. One is a system in which liquid crystals are sandwiched by two substrates having transparent electrodes and are driven by a voltage applied to the transparent electrodes, and light incident upon the liquid crystals and transmitted through the transparent electrode is modulated to achieve display. All of the products that are now available are based upon this system. Another one is a system in which liquid crystals are driven by an electric field which is nearly in parallel with the surface of a substrate between two electrodes that are formed on the same substrate, and light incident upon the liquid crystals through a gap between the two electrodes is modulated to provide display. Though no product which is based upon this system has yet been provided, it has a feature of a very wide viewing angle and a promising art in connection with active matrix liquid crystal display devices.
Features of the latter system have been disclosed in, for example, Japanese Patent Laid-Open No. 505247/1993, Japanese Patent Publication No. 21907/1988 and Japanese Patent Laid-Open No. 160878/1994.